Stereophonic piezoelectric bender-type transducer



Oct. 26, 1965 R. R. TEN EYCK 3,2 4,

STEREOPHONIC PIEZOELECTRIC BENDER-TYPE TRANSDUCER Filed OCT,- 22, 1959 2Sheets-Sheet l MN 54 I Tijll]. INVENTOR. TATE. Eoaem R TEN EYCK ATTORNEYOct. 26, 1965 R. R. TEN EYCK 3,214,525

STEREOPHONIC PIEZOELECTRIC BENDER-TYPE TRANSDUCER Filed Oct. 22, 1959 2Sheets-Sheet 2 152 756 f84 T5117. T3115. 1a?

IN V EN TOR.

204 TiclEEl ROBERT E TEN EYCK QTTOENEY United States Patent 3,214,525STEREOPHONIC PIEZOELECTRIC BENDER-TYPE TRANSDUCER Robert R. Ten Eyck,Metucheu, N.J., assignor to Gulton Industries, Inc., Metuehen, N.J., acorporation of New Jersey Filed Oct. 22, 1959, Ser. No. 848,116 9Claims. (Cl. 179-10041) My invention relates to stereophonic transducersand in particular to those stereophonic transducers which are formed offerroelectric ceramic material.

An important object of my invention is to provide a stereophonictransducer with relatively high sensitivity and low cross couplingbetween the channels.

It is a further object of my invention to provide such a transducerwhich has low mass, high capacity and high compliance.

It is a still further object of my invention to provide such atransducer which is simple and economical to produce.

These and other objects, advantages and features of my invention will beapparent during the course of the following discussion when taken inconjunction with the accompanying drawings wherein:

FIGURE 1 is an elevational view, partly in cross-section, of oneembodiment of my invention,

FIGURE 2 is an elevational view of the active ceramic element of FIGURE1,

FIGURE 3 is a cross-sectional view along the line 3-3 of FIGURE 2,

FIGURE 4 is a view similar to FIGURE 1 of a further embodiment of myinvention,

FIGURE 5 is a view similar to that of FIGURE 2 of the active ceramicelement of FIGURE 4,

FIGURE 6 is a view along the line 66 of FIGURE 4 viewed in the directionof the arrows,

FIGURES 7, 9, 11, 13, 15, and 17 are views similar to that of FIGURE 2showing various electrode arrangements and configurations of the activeceramic element used in the carrying out of the teachings of myinvention,

FIGURES 8, 10, 12, 14, 16, and 18 are cross-sectional views taken, inthe order listed, respectively as follows: along the line 88 of FIGURE7; along the line Iii-1t of FIGURE 9; along the line 12-12 of FIGURE 11;along the line 1414 of FIGURE 13; along the line 16-16 of FIGURE alongthe line 18-48 of FIG- URE 17,

FIGURE 19 is an exploded perspective view showing still anotherembodiment of my invention,

FIGURE 20 is an assembled perspective view of the embodiment of FIGURE19, and

FIGURE 21 is a schematic diagram showing the electrical connections madeto the electrodes of the active elements illustrated in the variousfigures.

In the drawings, wherein, for the purpose of illustration, are shownvarious embodiments of my invention and wherein like numerals are usedfor like parts throughout the same, the numeral generally designates astereophonic transducer of my invention. In FIGURE 1, transducer 40 isseen to comprise ferrolelectric ceramic element 42 which is in the formof a hollow cylinder provided with a longitudinal slit extendingthroughout the length thereof and to which have been applied outerelectrodes 44 and 45 (only one of which is shown in FIGURE 2 as 44),metallic torsion bar 50, plastic cap 46 and case 48. Affixed to element42 is cup 56 to which is afiixed stylus assembly 52. Stylii 54 and 54aare affixed to assembly 52 and are provided to enable the user to flipthe cartridge over when different stylus point radii are requireddepending on the record groove dimensions.

Electrode 47 on the inner surface of element 42 covers the completesurface so that in effect there are three electrodes on element 42;first, electrode 44 on the outer surface of element 42 as shown inFIGURE 2; second, electrode 45 similar in size and location to electrode44 on the outer surface of element 42 opposite electrode 44; and third,electrode 47 on the inner surface of element 42. Connection is made toelectrode 47 through torsion bar 50 as shown in FIGURE 1. If desired,two electrodes may be applied to theinner surface of element 42 so thatpairs are formed with the outer electrodes.

I have found that sufficient separation between the channels is achievedwhen using stereophonic pickups made in accordance with my invention toproduce excellent subjective results and statistical measurementscomparable with the stereophonic pickups now in use and publiclyaccepted.

Electrical connections are made as shown in FIGURE 21. The output of theright channel amplifier is connected between the common connection andthat marked RIGHT in the figure and the left channel amplifier isconnected between the common connection and that marked LEFT in thefigure. As can be seen in FIG- URE 21 the LEFT channel is connected toelectrode 44, the RIGHT channel is connected to outer electrode 45 (notshown in FIGURE 21) and the common connection is made to inner electrode47. The record groove in which stylus 54 rides is designated as 205.

Brass cup 56 of FIGURE 1 is used to couple the ceramic transducerelement 42 to the stylus assembly 52. The inside diameter of cup 56 issuch that element 42 is seated within cup 56 to provide just enoughclearance to apply bonding cement such as a nitrocellulose base cementto the combination so that the active ceramic element is securely bondedto the cup. The bonding cement is such that there is good physical andmechanical bonding between the element and the cup and good acoustictransmission and coupling between the ceramic element and the stylusassembly. Nonelectroded margin 43 is provided to prevent the brass cupfrom shorting electrode 44 to electrode 45.

FIGURES 4, 5 and 6 illustrate a further embodiment of my invention whichis very similar to the embodiment of FIGURES 1 through 3. The completeassembly, generally designated as 60, comprises a longitudinally split,hollow cylindrical ceramic element 62, case 68, plastic cap 66, metallictorsion bar 70 through which electrical connection is made to the innerelectrode, metallic bar 76, and stylus assembly 52. Electrode 64 isapplied to element 62 in any manner well-known in the art and the otherelectrodes needed to complete the device such as are shown in FIGURE 3are not shown in this particular embodiment. It should be noted that theceramic elements of FIGURES 2 and 5 are interchangeable and may be usedin either embodiment.

Metallic bar 76 is used to provide the necessary stylus to ceramiccoupling. In this embodiment, the bar is bonded to the inside of thetube and it is not necessary to provide insulation between the bar andthe inner electrode because the inner electrode is at ground potential.While I chose to use metal as the material for bar 76 because of theease of machining it, I have also found that a molded plastic such aspolyethylene is desirable because of its lower density and consequentlower mass per volume.

The various electrode ceramic element configurations shown in FIGURES 7through 18 may be used with either of the embodiments described above.The ceramic element of FIGURES 7 and 8 is designated 82 and it comprisesa hollow cylinder provided with a lower longitudinal slit throughout thelength thereof and an upper longitudinal slit which extends from thefree end thereof for substantially the length thereof, and has innerelectrode 87 and outer electrodes 84 and 85 applied thereto. In FIGURES9 and 10, the ceramic element is designated 102 and it corresponds inconstruction to ceramic element 82, and it has applied thereto outerelectrodes 104 and 105 and inner electrode 107. In FIGURES 11 and 12,the ceramic element is designated 122 and it corresponds in constructionto ceramic element 82, and it has applied thereto outer electrodes 124and 125 and inner electrode 127. The ceramic element of FIGURES 13 and14 is designated 142 and it comprises a hollow cylinder provided withupper and lower slits extending from the free end thereof forsubstantially the length thereof and has applied thereon outerelectrodes 144 and 145 and inner electrode 147. In FIGURES 1S and 16,the ceramic element is designated 162 and it corresponds in constructionto ceramic element 142, and it has applied thereon outer electrodes 164and 165 and inner electrode 167. The ceramic element of FIGURES 17 and18 is designated as 182 and it corresponds in construction to ceramicelement 82, and it has applied thereon outer electrodes 184 and 185 andinner electrode 187.

In FIGURES 19 and 20 there is shown a further embodiment of myinvention, generally designated as 200. It comprises hollowsemicylindrical ceramic elements 206 and 208 to each of which areapplied inner electrode 210 and outer electrode 212, rubber grommet 204and stylus assembly 202. Rubber grommet 204 is suitably bonded to stylusassembly 202 by means of nitrocellulose base cement and is then bondedto the inside of elements 206 and 208 by means of nitrocellulose basecement. Elements 206 and 208 are bonded to a torsion bar similar to bars50 and 70 by means of nitrocellulose base cement. The assembled elements206 and 208 provide a hollow cylinder provided with upper and lowerslits extending throughout the length thereof.

In FIGURE 21 there is shown still another embodiment of my invention inwhich a different stylus assembly 203 is bonded to the longitudinallysplit, hollow cylindrical, ceramic element 42 by means of anitrocellulose base cement.

The fiip over stylii, shown in the various figures, are provided topermit the reproduction of both monophonic and stereophonic recordingsWith the single assembly. In operation as a stereophonic reproducingtransducer, the stylus transmits the channel motion of the usual 45stereophonic record groove or channel to the ceramic element such thatthere is a mechanical stress produced in the respective channel volumesor portions of the ceramic element corresponding to the conformation ofthe original recording groove. As a result, the right portion of theelement responds to signals from a right motion of the stylus and theleft portion responds to signals from a left motion of the stylus. Thisis due to the fact that the ceramic element responds to the respective45 motions of the record groove or channel.

Due to the asymetrical construction of a split cylinder the resultantstrain due to the motion and stress applied thereto by the stylus isgreater in one half the element and the other for the 45 directions ofstress. This effect can be enhanced by electroding only in the region ofmaximum strain (near the top of the unit). Cross coupling through theunelectroded top region is only due to shear elasticity and notpiezoelectric effects and is generally small in ceramic transducers.

The electroding of FIGURES and 16, and 17 and 18 gives the bestsensitivity and channel separation. Quality of music reproduction is notlost with the other electroding configurations, and where a highcapacity is needed, the larger electroded area would be necessary andchannel separation could be improved by mechanical means.

While I have described my invention in terms of its use as astereophonic phonograph pickup, devices of my invention may also be usedas stereophonic record cutters since the device is a reversibletransducer. For reproduction of monophonic recordings the stylii areflipped over to proivde the appropriate stylus for the groove or channelof the monophonic record and the electrodes of the ceramic element areswitched to place them in the circuit of the amplifier to provide themonophonic reproduction.

I prefer to form the ceramic element for my invention of theferroelectric ceramics such as barium titanate, lead titanate-zirconateor similar materials polarized to be piezoelectric, but the element maybe formed of any other piezoelectric material having the sameelectromechanical properties as the foregoing materials.

While I have disclosed my invention in relation to specific examples andin specific embodiments, I do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of my invention.

Having thus described my invention, I claim:

1. A stereophonic transducer comprising a hollow, cylindrical,ferroelectric ceramic body, means for mounting said body at one end onlywith the other end free to move laterally said body being provided withat least one 10ngitudinal slit running from one end thereof forsubstantially the length of said body, at least three electrodes affixedto said body, one of said electrodes being placed on the outer surfaceof said body on one side of said slit, the second of said electrodesbeing placed on the outer surface of said body on the second side ofsaid slit, the third of said electrodes being placed on the innersurface of said body, a stylus atfixed to said body in alignment withthe slit at the free end thereof for laterally bending the body tooppositely stress the body between the first and third electrodes andbetween the second and third electrodes, and means for making electricalconnections to said electrodes.

2. A stereophonic transducer as described in claim 1 wherein said thirdelectrode is applied to the inner surface of said body substantiallyopposite said first electrode and including a fourth electrode appliedto the inner surface of said body substantially opposite said secondelectrode.

3. A stereophonic transducer comprising a hollow, cylindrical,ferroelectric ceramic body, means for mounting said body at one endthereof, said body being provided with a pair of oppositely placed,longitudinal slits running from the free end thereof for substantiallythe length of said body, two pairs of electrodes affixed to said body,one of said pairs of electrodes being placed between one side of saidslits on the inner and outer surfaces of said body, the other of saidpairs of electrodes being placed between the other side of said slits onthe inner and outer surfaces of said body, a stylus afiixed to said bodyin alignment with the slits at the free end thereof, and means formaking electrical connections to said pairs of electrodes.

4. A stereophonic transducer as described in claim 3 wherein each ofsaid electrodes covers substantially all the surface to which it isaffixed and which is between said pair of slits.

5. A stereophonic transducer as described in claim 3 wherein theelectrodes applied to the outer surfaces of said body are spaced fromthe open end of said slits and olccupy substantially all of thecircumference between said s its.

6. A stereophonic transducer as described in claim 5 wherein saidelectrodes occupy approximately one half of the circumference betweensaid slits.

7. A stereophonic transducer for use with a 45 stereophonic recordgroove comprising a hollow, cylindrical, ferroelectric ceramic body,means for mounting said body at one end thereof, said body beingprovided with at least one longitudinal slit running from the free endthereof for substantially the length of said body, at least threeelectrodes aflixed to said body, one of said electrodes, being placed onthe outer surface of said body on one side of said slit, the second ofsaid electrodes being placed on the outer surface of said body on thesecond side of said slit, the third of said electrodes being placed onthe inner surface of said body, a stylus aifixed to said body inalignment with the slit on the free end thereof and engageable in the 45stereophonic record groove for stressing the portions of the ceramicbody on opposite sides of the slit therein in accordance with theundulations on opposite sides of the 45 stereophonic record groove, andmeans for making electrical connections to said electrodes fortransmitting electrical signals in accordance with the stressing of saidportions of the ceramic body.

8. A stereophonic transducer as described in claim 7 wherein said thirdelectrode is applied to the inner surface of said body substantiallyopposite said first electrode and including a fourth electrode appliedto the inner surface of said body substantially opposite said secondelectrode.

9. A stereophonic transducer comprising a hollow, cylindrical,ferroelectric ceramic body, means for mounting said body at one end onlywith the other end free to move laterally, said body being provided Witha longitudinal slit running from the free end thereof for substantiallythe length of said body, three electrodes afiixed to said body, thefirst of said electrodes being placed on the outer surface of said bodyon one side of said slit, the second of said electrodes being placed onthe outer surface of said body on the other side of said slit, the thirdof said electrodes being placed on the inner surface of said body inradial alignment with both of said first and second electrodes, a stylusaffixed to said body in alignment with the slit at the free end thereoffor laterally bending the body to oppositely stress the body between thefirst and third electrodes and between the second and third electrodes,and means for making electrical connections to said electrodes.

References Cited by the Examiner UNITED STATES PATENTS 2,719,929 10/55Brown 179100.4l 2,928,069 3/60 Petermann 179-100.41 2,944,117 7/60 Gray179100.41

IRVING L. SRAGOW, Primary Examiner.

ROBERT H. ROSE, JOHN P. WILDMAN, Examiners.

1. A STEREOPHONIC TRANSDUCER COMPRISING A HOLLOW, CYLINDRICAL,FERROELECTRIC CERAMIC BODY, MEANS FOR MOUNTING SAID BODY AT ONE END ONLYWITH THE OTHER END FREE TO MOVE LATERALLY SAID BODY BEING PROVIDED WITHAT LEAST ONE LONGITUDINAL SLIT RUNNING FROM ONE END THEREOF FORSUBSTANTIALLY THE LENGTH OF SAID BODY, AT LEAST THREE ELECTRODES AFFIXEDTO SAID BODY, ONE OF SAID ELECTRODES BEING PLACED ON THE OUTER SURFACEOF SAID BODY ON ONE SIDE OF SAID SLIT, THE SECOND OF SAID ELECTRODESBEING PLACED ON THE OUTER SURFACE OF SAID BODY ON THE SECOND SIDE OFSAID SLIT, THE THIRD OF SAID ELECTRODES BEING PLACED ON THE INNERSURFACE OF SAID BODY, A STYLUS AFFIXED TO SAID BODY IN ALIGNMENT WITHTHE SLIT AT THE FREE END THEREOF FOR LATERALLY BENDING THE BODY TOOPPOSITELY STRESS THE BODY BETWEEN THE FIRST AND THIRD ELECTRODES ANDBETWEEN THE SECOND AND THIRD ELECTRODES, AND MEANS FOR MAKING ELECTRICALCONNECTIONS TO SAID ELECTRODES.